Currently your question is a "do this job for me"-question. Please show us your research effort: What do you think would be usable, what have you already tried and why did it fail, etc.
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kaiser♦Sep 24 '12 at 12:40

You really can just make category-slug.php for the category and be done with it. Unless you're trying to say that you want the category page to show that category, and none of the posts that may be in children or other categories.